Start the migration of passwords from the Keychain.

chrome/browser/password_manager/password_store_proxy_mac.h

Index: chrome/browser/password_manager/password_store_proxy_mac.h
diff --git a/chrome/browser/password_manager/password_store_proxy_mac.h b/chrome/browser/password_manager/password_store_proxy_mac.h
index 67029cf3ceec3be5219ef9f0993db80496d74d6f..fffbc8ef805774f6d1fa647df36aa4f14de23bda 100644
--- a/chrome/browser/password_manager/password_store_proxy_mac.h
+++ b/chrome/browser/password_manager/password_store_proxy_mac.h
@@ -5,8 +5,12 @@
 #ifndef CHROME_BROWSER_PASSWORD_MANAGER_PASSWORD_STORE_PROXY_MAC_H_
 #define CHROME_BROWSER_PASSWORD_MANAGER_PASSWORD_STORE_PROXY_MAC_H_
 
+#include <deque>
+
+#include "base/prefs/pref_member.h"
 #include "base/threading/thread.h"
 #include "components/password_manager/core/browser/password_store.h"
+#include "components/password_manager/core/common/password_manager_pref_names.h"
 
 namespace crypto {
 class AppleKeychain;
@@ -28,7 +32,8 @@ class PasswordStoreProxyMac : public password_manager::PasswordStore {
   PasswordStoreProxyMac(
       scoped_refptr<base::SingleThreadTaskRunner> main_thread_runner,
       scoped_ptr<crypto::AppleKeychain> keychain,
-      scoped_ptr<password_manager::LoginDatabase> login_db);
+      scoped_ptr<password_manager::LoginDatabase> login_db,
+      PrefService* prefs);
 
   bool Init(const syncer::SyncableService::StartSyncFlare& flare) override;
   void Shutdown() override;
@@ -47,7 +52,13 @@ class PasswordStoreProxyMac : public password_manager::PasswordStore {
   password_manager::PasswordStore* GetBackend() const;
 
   // Opens LoginDatabase on the background |thread_|.
-  void InitOnBackgroundThread();
+  void InitOnBackgroundThread(password_manager::MigrationStatus status);
+
+  // Writes status to the prefs.
+  void UpdateStatusPref(password_manager::MigrationStatus status);
+
+  // Executes |pending_ui_tasks_| on the UI thread.
+  void FlushPendingTasks();
 
   // PasswordStore:
   void ReportMetricsImpl(const std::string& sync_username,
@@ -82,11 +93,20 @@ class PasswordStoreProxyMac : public password_manager::PasswordStore {
 
   // The login metadata SQL database. If opening the DB on |thread_| fails,
   // |login_metadata_db_| will be reset to NULL for the lifetime of |this|.
+  // The ownership maybe transferred to |password_store_simple_|.

[vabr (Chromium), 2015/07/06 09:50:19]

nit: maybe -> may be
(otherwise the verb is missing)

[vasilii, 2015/07/06 13:57:57]

Done.

   scoped_ptr<password_manager::LoginDatabase> login_metadata_db_;
 
   // Thread that the synchronous methods are run on.
   scoped_ptr<base::Thread> thread_;
 
+  // Current migration status for the profile.
+  IntegerPrefMember migration_status_;
+
+  // List of task filled by InitOnBackgroundThread. They can't be just posted to

[vabr (Chromium), 2015/07/06 09:50:19]

After clarifying the concurrency concerns with you off-line, Vasilii, I think
this comment needs to specifically point out that to avoid concurrent access to
the queue:
(1) after InitOnBackgroundThread is run once, the queue may not be modified on
the background thread any more
(2) Shutdown() flushes the queue _after stopping the background thread_

Mentioning (1) seems really important. Alternatively you can just add "only" to
"filled by InitOnBackgroundThread", but that's a stronger statement and could be
confusing in some future refactoring.

(2) is not crucial, but helps to understand the design.

[vabr (Chromium), 2015/07/06 09:50:19]

nit: task -> tasks

[vasilii, 2015/07/06 13:57:57]

Done.

[vasilii, 2015/07/06 13:57:58]

Done.

+  // the UI thread because the message loop can shutdown before executing them.

[vabr (Chromium), 2015/07/06 09:50:19]

nit: shutdown -> shut down
(the verb not the noun)

[vasilii, 2015/07/06 13:57:58]

Done.

+  // If this is the case then Shutdown() flushes the tasks.
+  std::deque<base::Closure> pending_ui_tasks_;
+
   DISALLOW_COPY_AND_ASSIGN(PasswordStoreProxyMac);
 };